Process of making a photoconductive material of cadmium sulfide and cadmium carbonate

ABSTRACT

A process for making a photoconductive material which comprises treating a photoconductive material of fine powder particles composed principally of cadmium sulfide and cadmium carbonate with a silicon compound after the photoconductive material has been washed in enough water to remove the isolated water soluble matter is disclosed.

United States Patent [1 1 Yamada et a1.

[ Feb. 18, 1975 PROCESS OF MAKING A PHOTOCONDUCTIVE MATERIAL OF CADMIUM SULFIDE AND CADMIUM CARBONATE [75] Inventors: Yoshihiko Yamada; Katsuo Makino,

both of Odawara, Japan [73] Assignee: Fuji Photo Film Co., Ltd.,

Kanagawa, Japan [22] Filed: Apr. 20, 1972 [21] Appl. No.: 245,811

[30] Foreign Application Priority Data Apr. 20, 1971 Japan' 46-24968 [52] U.S. Cl. 96/] PC, 252/501 [51] Int. Cl .i G03g 5/04 [58] Field of Search 252/501; 96/1 PC, 1.5

[56] References Cited UNITED STATES PATENTS 3,155,504 11/1964 Damm el al. 252/501 3,591,028 11/1976 Makino 252/501 3,681,067 8/1972 Hanada .4 96/l.5

Primary ExaminerNorman'G. Torchin Assistant Examiner-John L. Goodrow Attorney, Agent, or FirmJ. T. Martin; Gerald J; Ferguson, Jr.; Joseph J. Baker [57] ABSTRACT 20 Claims, 1 Drawing Figure IP (vom TEMPERATURE 1C) PATENTEU E 1875 TEMPERATURE (C) PROCESS OF MAKING A PHOTOCONIDUCTIVE MATERIAL OF CADMIUM SULFIDE AND CADMIUM CARBONATE BACKGROUND OF THE INVENTION process in which the material produced is an especially suitable photoconductive materialfor use as a photosensitive part in an electrophotography device used in an atmosphere of high temperature and humidity.

2. Description of the Prior Art Many photoconductive materials are known publicly and their utilization is diversified. Fine powder particles of photoconductive materials are used not only in the manufacture of photocells, photoamplifiers or photo-image-converters, but also as photoconductive pigments for the pigment-resin type of electrophotography photosensitive material. The pigment-resin type photosensitive material is one in which fine powder particles of a photoconductive material dispersed in the resin are applied on a support. Typical photoconductive materials for this purpose are zinc oxide and cad m-iumsulfide. But a pigment-resin type photosensitive material containing zinc oxide generally has large light fatigue and is unsuitable as a photosensitive material which is to be used continuously and repeatedly. On the other hand, the photosensitive layer in a film which is formed of fine powder particles of cadmium sulfide,

tends to have a lowered sensitivity asthe thickness of the film increases. Consequently, if the thickness of the film is increased to raise the earliest surface potential in order to give a full electrostatic contrast to the electrostatic latent image formed on the photosensitive layer, disadvantages in that the sensitivity is lowered and the reaction rate of the photoconductive current is slow occur.

The present inventor previously found that the photoconductive material, the physico-chemical combination of cadmium sulfide and cadmium carbonate, CdS.nCdCO (O n s 4), had superior properties as the electrophotography sensitive material. The photosensitive material has the characteristic that it can be either positively or negatively charged and regardless of how charged is almost equally sensitive. Further by adding selenium or a selenic compound, iodine or an iodic compound, as disclosed in Japanese Patent Application Nos. 59,l65/l965, 23,546/1967, and 6,475/1968 a metallic salt of a fatty acid as disclosed in Japanese Patent Application No. 62,202/1968 or a coloring matter to the photoconductive material, the electrophotography property has been found to be improved.

But when the photoconductive material is used in an atmosphere of high temperature and humidity, the surface resistivity and the volume resistivity of the photosensitive layer have sometimes been reduced and as a result the electrophotography properties have been deteriorated. This has been found to be caused by the presence of a water soluble compound at isolated positions within the photoconductive material, for example, a water soluble iodic compound is mixed with the fine powder particles of cadmium sulfide and cadmium carbonate when they are manufactured or various additives are used. Then the material is washed in enough water to remove such water soluble matter, but there is a tendency for the other electrophotography properties to be worsend. For example, there is the disadvan tage that the density of the electrophotography image obtained using a fully washed photoconductive material is lower than that obtained with unwashed material.

Accordingly an object of this invention is to provide a process for making a photoconductive material in which the electrophotography characteristics are not deteriorated even in an atmosphere of high temperature and humidity. Another object is to provide a photoconductive material having superior electrophotography propertieseven in an atmosphere ofhigh temperature and humidity.

SUMMARY or THE INVENTION These objects are attained by treating a photoconductive material composed principally of cadmium sulfide and cadmium carbonate which has been previously washed in water with a silicon compound. More specifically, according to the present invention, after the photoconductive material of fine powder particles composed principally of cadmium sulfide and cadmium carbonate have been washed in enough water to remove the isolated water soluble matter, by treating this material with a silicon compound it is possible to obtain a photoconductive materialwhich retains good electrophotography properties even in an atmosphere of high temperature and humidity.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING DETAILED DESCRIPTION OF THE INVENTION The silicon compounds which can be employed in the present invention are those materials variously called silane coupling agent, carbon functional silane or silicon of reactivity, including such compounds having the following general formula:

wherein, R represents a substituted or a nonsubstituted alkyl group, a cycloalkyl group, an alkenyl group or an aryl group, while X X and X which may be the same or different, each representsa halogen atom or an alcoxyl group. Alkyl groups such as methyl, ethyl, propyl, butyl, amyl and the like, substituted alkyl groups such as carboxy substituted alkyl group, hydroxy substituted alkyl groups; chlorosubstituted alkyl groups and the like, cycloalkyl groups such as substituted and unsubstituted cyclohexyl groups, alkenyl groups such as vinyl, propenyl and the like, alkoxy groups such as methoxy, ethoxy, propoxy, butoxy and the like, aryl groups such as phenyl, tolyl, xylyl, biphenyl and the like and halogens such as chlorine bromine and iodine are suitable as substituents in the hereinbefore described silicon compound.

Suitable specific silicon compounds, for example, are as follows: n-propyltrichlorosilane, nbutyltrichlorosilane, phenyltrichlorosilane, methyltrimethoxysilane, phenyltrimethoxysilane, trimethoxysilyl-propylethylenediamine, y-methacryloxypropyltrimethoxysilane, y-glycidoxypropyltrimethoxysilane, vinyltrichlorosilane, chloropropyltrimethoxysilanevinylt riethoxysilane, vinyltris(B-methoxyethoxy) si lane, and B-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

The method of treating the fine powder particles of the photoconductive material with the silicon compound can vary. For example, the'fine powder particles can be dispersed ina solvent such as an alcohol the silicon compound added, and the alcohol removed. Need less to say, other suitable methods such as treatment of the photoconductive material with a vapor of the silicon compound can readily be employed.

The amount of silicon compound usually used in the solution employed in treating the photosensitive material is that amount of silicon compound which will result in the prepared photosensitive material containing from about 0.1 to 5%, perferably from about 0.5 to about 5%, by weight of the silicon compound.

The washing conducted before the treatment with the silicon compound is to remove the isolated water soluble matter from the photoconductive material. Therefore, the method whereby the washing is conducted can vary and the choice ofa suitable one can be made by the producer. 1 The photoconductive material produced in accordance with the present invention, has the advantage that a clear image with no lowered image density and little foggy background is obtained even when employed in an atmosphere of high temperature and humidity as an electrophotography sensitive material. Also a photosensitive material having a stable electrophotography property whether charged positively or negatively is provided. By adding a dyestuff to the treated fine powder particles of the photoconductive material it is possible to increase the intrinsic sensitivity or to additionally increase the range of spectral sensitivity. There are many such dyestuffs, for example, dyestuffsof the phthalein group (Eosine, Roseb'engal, Fluorescein, Floxin, Ethyleosine), the triphenylmethane group (Malachite green, Crystal violet, Brilliant green). the cyanin group (Dicyanin, Cryptocyanin, Pinacyanol, Neocyanin, Merocyanin), and Rhodamine and Methylmium sulfide to be employed in the present invention and their manufacturing process, and the various additives which are used to improve the properties of these particles and the method of their addition, these are previously disclosed in patents by the present inventor. See Japanese Patent No. 557,554 (Application No. 32,170/1965 and Publication No. 32,170/1965) and Japanese Patent No. 567,565 (Application No. 47,045/1965 and Publication No. 23,775/1969).

Now a more detailed explanation will be made of this invention by reference to preferred embodiments of the present invention.

EXAMPLE 1 added to liquid A and stirred to make a suspension. in

to this suspension liquid B was added dropwise slowly to form a white sediment of cadmium carbonate. Further, liquid C was'added dropwise in to the Aerosil and cadmium carbonate dispersion and suspension, to convert some of the cadmium carbonate into cadmium sulfide.

washed sufficiently in water, dried for about 30 hours at 70C. Following the drying, a low temperature baking treatment was conducted on it for about 24 hours at 200C. The fine powder obtained is designated D powder".

20 g. of cadmium iodide dissolved in ethyl alcohol were added dropwise in an agitated solution in which 100 g. of the D powder had been dispersed in ethyl al cohol, to have the D powder adsorbed by the cadmium iodide. The solution, after standing for several hours, was decanted removing the supernatant liquid and the solid material was dried for about.24 hours at 70C. The dried material was heated for about 24 hours at 200C. The obtained fine powder is designated E powene Blue, in an amount of from about 0.001 to 1% by weight based on the weight of the photosensitive compound.

The thus obtained fine powder particles of the photoconductive material can be employed as a photoconductive pigment for the pigment-resin type photosensitive material. In-this case, it is desired that the particle diameter be less than 5 micron. Also as binders used in this case, those conventionally employed in the manufacture of the pigment-resin type photosensitive material can suitably be selected, such as polymethylmethacrylates, polyacrylates, polystyrenes, styrene copolymers, vinyl acetate copolymers, melamine resins, urea resins, alkyd resins, epoxy resins and ins.

As regards the fine powder particles of photoconductive material which are composed principally of cadpolyurethane resder.

g. of E powder was will dispersed in 400 ml of water having a volume resistance of greater than 10 0 cm, and after standing 30 minutes, the solids settled and the supernatant liquid was removed. This treatment was repeated four times, and the precipitated powder was dried for one night at 80C. The obtained powder is designated F powder 2g of trimethoxysilylpropylethylenediamine dissolved in ethyl alcohol were added dropwise into an agitated solution of l00g of the F powder dispersed in ethyl alcohol, to have the F powder adsorbed by the trimethyoxysilylpropylethylenediamine. The liquid was removed from the dispersionand the solid was dried for about 24 hours at 70C and then it was heat treated for 2 hours at C. The obtained powder is designated G powder 1 After the G powder was mixed and dispersed with 2g of copper stearate, 50g of a thermosetting acrylic resin (Magicron 200 produced by the Kansai Paint Co., Ltd, Japan) and an organic solvent, a thinner for Magicron 200, this was applied to the surface of an aluminum pipe, 200 mm in diameter and 300 mm in length, at a thickness of 40 microns. This pipe, after being dried for The thus formed yellow sediment was, after being- 30 minutes at 70C, was subjected to a hardening treatment for 30 minutes at 150C to produce an electro' photography sensitive material capable of being used repeatedly. The obtained sample is designated No. 1.

.In the same way, E powder and F powder were used in place of the G powder to produce additional samples. These samples are designated respectively No.2 and No. 3.

' Each of the samples, after a corona current of 60 microampere was given at the distance of one centimeter from the surface of the pipe which was rotated at the speed of seconds for one rotation, was evaluated by measuring the surface potential (I?) about 2 seconds after charging. The thermometric dependence of the IP of samples No. 1 and No. 2 taken in a humidity of 90%, is shown in the accompanying drawing. In the drawing curve 1 is for sample No. l and curve 2 is for sample No. 2. Sample No. 3 gave almost the same curve as sample No. 1. It can be seen from the drawing that an electrophotography sensitive material employing the photoconductive material produced according to the present invention, possesses outstanding characteristics even in an atmosphere of high temperature and humidity.

Then samples No. l No. 3 were used each for reproduction using coonventional electrophotography processing steps of being charged, exposed, developed and reproduced. In the negatively charged case, sample No. 2 gave a clear image at a low humidity condition but almost no image at a high humidity condition was obtained. Also sample No. 3 gave only a light image at a low humidity condition.'On the contrary sample No. 1 could reproduce a very clear image even at the high humidity condition of 90% RH at 35C. In the positively charged case, while sample No. 2 gave only an image with a high background density, sample No. 1 gave a clearimage with a low background density. The results'reported above definitely demonstrate that the silicon compound employed in the present invention is very effective.

Example 2 When vinyltriethoxysilane was employed in place of the trimethoxysilylpropylethylenediamine used in Example I, almost the same results were obtained as in Example 1.

Example 3 When vinyltris(B-methoxyethoxy)silane was employed in place of the trimethoxysilylpropylethylenediamine used in Example 1, almost the same results were obtained as in Example 1.

Example 4 When ,B-(3,4-epoxycyclohexyl)ethyltrimethoxysilane was employed in place of the trimethoxysilylpropylethylenediamine used in Example 1, almost the same results were obtained as in Example 1.

Example 5 When y-methacryloxypropyltrimethoxysilane was employed in place 'of the trimethoxysilylpropylethylenediamine used in Example 1, almost the same results were obtailed as in Example 1. while the invention has been described in detail and in terms of various em bodiment thereof, it will be apparent that various changes and modifications can be made therein without departing from the spirit and the scope thereof.

What is claimed is:

l. A process for making a photoconductive material which comprises preparing a photoconductive material of fine powder particles principally ofcadmium sulfide and cadmium carbonate in physico-chemical combination, washing said photoconductive material with water to remove water soluble matter, and subsequently adsorbing a silicon compound on said washed photoconductive material so that said photoconductive material contains about 0.1 to 5% weight of said silicon compound whereby a clear image of'high density and little background fog may be obtained on said photoconductive material even in an atmosphere of high temperature and humidity.

2. The process of claim 1, wherein said silicon compound has the general formula:

wherein R represents a substituted or a non-substituted alkyl group, cycloalkyl group, an alkenyl group or an aryl group, and wherein X X and X which may be the same or different, each represents a halogen atom or an alkoxyl group.

3. The process of claim 2, wherein said silicon compound is trimethoxysilylpropylethylenediamine.

4. The process of claim 1, wherein said silicon compound employed in such an amount that the photoconductive material contains from about 0.5 to about 5% by weight. g g

5. The process of claim 1, wherein said photoconductive material comprises CdS.nCdCO in which n is greater than 0 and less than or equal to 4.

6. The process of claim 2, wherein said photoconductive material comprises CdS.nCdCO in which n is greater than 0 and less than or equal to 4.

7. The process of claim 3, wherein said photoconduc tive material comprises CdS.nCdCO in which n is greater thanO and less than or equal to 4.

8. The process of claim 4, wherein said photoconductive material comprises CdS.nCdCO in which n is greater than 0 and less than or equal to 4.

' 9. The process of claim 1, wherein said photoconduc tive material additionally contains selenium or a selenic compound.

10. The process of claim 1, wherein said photoconductive material additionally contains iodine or an iodic compound.

11. A photoconductive material prepared in accordance with the process of claim 1.

12. A photosensitive layer comprising the photoconductive material of claim 11 dispersed in a binder.

13. An electrophotography sensitive material comprising the photosensitive layer of claim 12 applied on a support.

14. The photosensitive layer of claim 12, wherein said photosensitive layer additionally contains a metallic salt of a fatty acid.

15. the photosensitive layer of claim 12, wherein said photosensitive layer additionally contains a sensitizing dyestuff.

19. The photosensitive layer of claim 12, wherein the particle diameter of said photoconductive material is less'than 5 microns.

20. A process as in claim 6 wherein said silicon compound is about 0.5 to about 5% by weight of said photoconductive material and the particle diameter of said photoconductive material is less than 5 microns. 

1. A PROCESS FOR MAKING A PHOTOCONDUCTIVE MATERIAL WHICH COMPRISES PREPARING A PHOTOCONDUCTIVE MATERIAL OF FINE POWDER PARTICLES PRINCIPALLY OF CADMIUM SULFIDE AND CADMIUM CARBONATE IN PHYSICO-CHEMICAL COMBINATION, WASHING SAID PHOTOCONDUCTIVE MATERIAL WITH WATER TO REMOVE WATER SOLUBLE MATTER, AND SUBSEQUENTLY ABSORBING A SILICON COMPOUND ON SAID WASHED PHOTOCONDUCTIVE MATERIAL SO THAT SAID PHOTOCONDUCTIVE MATERIAL CONTAINS ABOUT 0.1 TO 5% WEIGHT OF SAID SILICON COMPOUND WHEREBY A CLEAR IMAGE OF HIGH DENSITY AND LITTLE BACKGROUND FOG MAY BE OBTAINED ON SAID PHOTOCONDUCTIVE MATERIAL EVEN IN AN ATMOSPHERE OF HIGH TEMPERATURE AND HUMIDITY.
 2. The process of claim 1, wherein said silicon compound has the general formula:
 3. The process of claim 2, wherein said silicon compound is trimethoxysilylpropylethylenediamine.
 4. The process of claim 1, wherein said silicon compound employed in such an amount that the photoconductive material contains from about 0.5 to about 5% by weight.
 5. The process of claim 1, wherein said photoconductive material comprises CdS.nCdCO3 in which n is greater than 0 and less than or equal to
 4. 6. The process of claim 2, wherein said photoconductive material comprises CdS.nCdCO3 in which n is greater than 0 and less than or equal to
 4. 7. The process of claim 3, wherein said photoconductive material comprises CdS.nCdCO3 in which n is greater than 0 and less than or equal to
 4. 8. The process of claim 4, wherein said photoconductive material comprises CdS.nCdCO3 in which n is greater than 0 and less than or equal to
 4. 9. The process of claim 1, wherein said photoconductive material additionally contains selenium or a selenic compound.
 10. The process of claim 1, wherein said photoconductive material additionally contains iodine or an iodic compound.
 11. A photoconductive material prepared in accordance with the process of claim
 1. 12. A photosensitive layer comprising the photoconductive material of claim 11 dispersed in a binder.
 13. An electrophotography sensitive material comprising the photosensitive layer of claim 12 applied on a support.
 14. The photosensitive layer of Claim 12, wherein said photosensitive layer additionally contains a metallic salt of a fatty acid.
 15. the photosensitive layer of claim 12, wherein said photosensitive layer additionally contains a sensitizing dyestuff.
 16. The photosensitive layer of claim 1, wherein said photosensitive layer additionally contains, a sensitizing dyestuff.
 17. The process of claim 1 wherein said silicon compound is added to the fine powder particles in the form of a vapor thereof.
 18. The process of claim 17, wherein said fine powder particles are dispersed in an alcohol.
 19. The photosensitive layer of claim 12, wherein the particle diameter of said photoconductive material is less than 5 microns.
 20. A process as in claim 6 wherein said silicon compound is about 0.5 to about 5% by weight of said photoconductive material and the particle diameter of said photoconductive material is less than 5 microns. 